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Single crystals of the lithium-ion conductor Li10GeP2S12 have been successfully grown by the self-flux method and are studied by means of X-ray diffraction and impedance spectroscopy. The weak anis...

Single crystals are indispensable for understanding the fundamental properties of materials, although obtaining them are often challenging. To investigate the magnetic properties of a kagome-lattice antiferromagnet, we have performed a topochemical crystal transformation from a copper mineral volborthite with a distorted kagome lattice into another copper mineral vesignieite with an almost perfect kagome lattice. A millimeter-sized crystal of vesignieite, which is difficult to prepare via direct chemical reactions, has been successfully obtained. Magnetization measurements on the crystals reveal a unique magnetic order with weak-ferromagnetic moments lying within the kagome plane and successive anomalies in the magnetization curve, which would give important information on the magnetic order of the kagome-lattice antiferromagnet. The present results demonstrate a novel route via the topochemical crystal transformation in preparing a hard-to-obtain crystal.

We have studied electronic properties of perovskite oxyhydrides ATiO3–xHx (A = Ba, Sr). Epitaxial thin films of ATiO3–xHx with various hydride compositions, up to x = 0.58 for Ba and x = 0.45 for Sr, are prepared by the low-temperature CaH2 reduction of the corresponding oxide films deposited on (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates by pulsed laser deposition. Resistivity measurements for A = Sr show a metallic phase over a wide range of H– composition, implying a substantial stabilization of H 1s orbitals that should be distributed over O 2p orbitals. On the other hand, for A = Ba, a semiconducting behavior is seen up to ∼5–8% of H– substitution. Interestingly, a similar contrasting behavior is observed in a Nb-substituted BaTiO3 and SrTiO3, which suggests that a local cation–off centering in lightly doped Ba films creates in-gap states in the band structure (as opposed to the Sr films), hindering the electron transport.

In this report, we demonstrate a novel synthesis method to obtain reduced titanium oxides with monolithic shape and with a well-defined hierarchically porous structure from the titanium-based network bridged with ethylenediamine. The hierarchically porous monoliths are fabricated by the nonhydrolytic sol–gel reaction accompanied by phase separation. This method allows a low-temperature crystallization into Ti4O7 and Ti3O5 at 800 and 900 °C, respectively, with N-doped carbon. These reduced titanium oxides are well-doped with N atoms even under argon atmosphere without NH3, which accounts for the low-temperature reduction. The resultant monolithic materials possess controllable macropores and high specific surface area together with excellent electric conductivity up to 230 S cm–1, indicating promise as a conductive substrate that can substitute carbon electrodes.